The University of Southampton
University of Southampton Institutional Repository

Aft fan noise reduction with a lined afterbody

Aft fan noise reduction with a lined afterbody
Aft fan noise reduction with a lined afterbody
Aft fan noise is becoming a more dominant source as engine bypass ratio is increased and improved methods are for required for its control. Acoustic linings are an effective means of reducing internally generated noise and bypass liners are especially effective in attenuating aft fan noise. Previous calculations have shown that as the fan noise emerges from the bypass exhaust nozzle, a significant part of the sound field radiates directly out through the shear layer but there is also another propagation path, along which the sound field is first reflected from the hard ‘afterbody’ before it propagates out to the far field. It has been suggested that if the afterbody were acoustically lined, it would reduce the strength of that reflected field and hence the far field noise level. Here we describe results from some preliminary tests on a rig, using scaled, locally reacting, linear SDOF acoustic linings to simulate the conventional, internal bypass liners and also the new external Afterbody Liner (AL). The measured data from this ‘No-flow’ rig indicate that up to 3 dB PWL insertion loss can be achieved with an AL in addition to that achieved with conventional bypass liners. Calculations agree well with the measured PWL insertion loss spectrum although the measured SPL reductions are not so well predicted at some angles. This novel application of conventional liner technology to the external afterbody of an engine nacelle may provide some significant reductions in aft broadband fan noise levels although it should be emphasised that the results obtained so far are without flow.
Tester, B.J.
1bd4a793-131b-4173-93cc-3eca70b2d116
De Mercato, L.
0be28cbb-dae1-49b8-847b-62683ef86231
Holland, K.
90dd842b-e3c8-45bb-865e-3e7da77ec703
Tester, B.J.
1bd4a793-131b-4173-93cc-3eca70b2d116
De Mercato, L.
0be28cbb-dae1-49b8-847b-62683ef86231
Holland, K.
90dd842b-e3c8-45bb-865e-3e7da77ec703

Tester, B.J., De Mercato, L. and Holland, K. (2007) Aft fan noise reduction with a lined afterbody. 13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference), Rome, Italy. 21 - 23 May 2007. 8 pp .

Record type: Conference or Workshop Item (Paper)

Abstract

Aft fan noise is becoming a more dominant source as engine bypass ratio is increased and improved methods are for required for its control. Acoustic linings are an effective means of reducing internally generated noise and bypass liners are especially effective in attenuating aft fan noise. Previous calculations have shown that as the fan noise emerges from the bypass exhaust nozzle, a significant part of the sound field radiates directly out through the shear layer but there is also another propagation path, along which the sound field is first reflected from the hard ‘afterbody’ before it propagates out to the far field. It has been suggested that if the afterbody were acoustically lined, it would reduce the strength of that reflected field and hence the far field noise level. Here we describe results from some preliminary tests on a rig, using scaled, locally reacting, linear SDOF acoustic linings to simulate the conventional, internal bypass liners and also the new external Afterbody Liner (AL). The measured data from this ‘No-flow’ rig indicate that up to 3 dB PWL insertion loss can be achieved with an AL in addition to that achieved with conventional bypass liners. Calculations agree well with the measured PWL insertion loss spectrum although the measured SPL reductions are not so well predicted at some angles. This novel application of conventional liner technology to the external afterbody of an engine nacelle may provide some significant reductions in aft broadband fan noise levels although it should be emphasised that the results obtained so far are without flow.

Full text not available from this repository.

More information

Published date: May 2007
Additional Information: AIAA 2007-3527
Venue - Dates: 13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference), Rome, Italy, 2007-05-21 - 2007-05-23

Identifiers

Local EPrints ID: 50432
URI: https://eprints.soton.ac.uk/id/eprint/50432
PURE UUID: 63e302cb-bda6-4464-9105-c137bdd14847
ORCID for K. Holland: ORCID iD orcid.org/0000-0001-7439-2375

Catalogue record

Date deposited: 26 Feb 2008
Last modified: 14 Mar 2019 01:54

Export record

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×